Find the value of the ratio.
Need help, please - and also need explanation.

Find the multiplicative inverse of 8-12i

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics